Objective 5.5

Plan Security for Wireless Networks

18-29

Objective 5.5

Plan Security for Wireless

Networks

Wireless networking has existed for many years, but it is only recently, with the publi-

cation of the 802.11 series of standards by the Institute of Electrical and Electronic Engi-

neers (IEEE), that wireless local area networking (WLAN) technologies have

become mainstream products. The 802.11b standard defines a WLAN technology run-

ning at speeds up to 11 megabits per second (Mbps). This was the first affordable wire-

less standard to provide performance comparable to that of a cabled LAN. The 802.11a

and 802.11g standards provide wireless networking at greater speeds, up to 54 Mbps.

WLANs can use two topologies: ad hoc and infrastructure. An ad hoc topology con-

sists of two or more computers equipped with wireless network interface adapters that

communicate directly with each other. An infrastructure topology consists of wire-

less computers that communicate with an access point, which provides a connection

to a standard cabled network. An access point is a WLAN transceiver that is also

attached to the cabled network, using a standard Ethernet (or other data-link layer pro-

tocol) connection. Wireless systems in an infrastructure topology can communicate

with each other, but they do so through the access point; they cannot communicate

directly.

Because WLAN network interface adapters and access points transmit their network

packets using radio signals, they present a significant natural security risk. WLAN sig-

nals are omnidirectional, extending to the specified range of the equipment. Any com-

patible device within transmission range can therefore transmit and receive the WLAN

signals, enabling an unauthorized user to connect to the network or capture the pack-

ets transmitted by other users, compromising the data inside. Depending on the range

of your equipment and where you locate your access points, unauthorized users might

even be able to access your WLAN from outside the building, unless you take steps to

protect the network.

To provide security for a wireless network, you must first create an environment in

which users are authenticated and authorized before they are able to send data to and

receive it from an access point. Authentication and authorization prevent unknown

users from connecting to the wireless network, but they do not prevent eavesdroppers

from capturing the data packets transmitted by wireless systems. To do this, you must

configure the wireless devices to encrypt all the data they transmit. The most com-

monly used security mechanisms on WLANs are the following: